Water based ink and water based pigment ink having metallic lustrous color for ballpoint pen

ABSTRACT

Provided is a water based ink having a metallic lustrous color using an aluminum powder for a ballpoint pen which does not allow a discharging amount to reduce and splitting to occur. This water based ink contains an aluminum paste prepared by wetting aluminum powder in advance with at least one solvent selected from glycol ethers and glycols, a thickener, a water-soluble organic solvent and water. Further, provided is a water based pigment ink having a metallic lustrous color for a ballpoint pen in which an aluminum powder and a pigment are used and which allows the colorant to provide a well developed metallic lustrous color and can be used to draw beautiful lines. This water based pigment ink contains an aluminum powder, a water-soluble organic solvent, a pigment, a thickener and a resin emulsion.

TECHNICAL FIELD

The present invention relates to a water based ink and a water basedpigment ink having a metallic lustrous color for a ballpoint pen.

BACKGROUND ART

Disclosed in Japanese Patent Application Laid-Open No. Hei 7-145339 is awater based metallic lustrous color ink for a ballpoint pen whichcontains aluminum powder, natural polysaccharides, a water-solubleorganic solvent and water and has a viscosity of 100 to 1500 poise andin which a ratio of a viscosity at 1 rpm to a viscosity at 10 rpm is 3.0or more and in which a quality changes less even after storing over anextended period of time and a discharging property of the ink in aball-rotating part of the tip of the ballpoint pen is good. Further, itis described therein that "in order to provide the line with a metalliclustrous color, aluminum powder as a colorant can be used in combinationwith known water-soluble dyes such as acidic dyes, basic dyes and directdyes", but no specific examples are disclosed.

However, the ink described in preceding Japanese Patent ApplicationLaid-Open No. Hei 7-145339 is made by blending 0.7 to 10 parts by weightof natural polysaccharides for thickening, 5 to 40 parts by weight of awater-soluble organic solvent and 2 to 15 parts by weight of aluminumpowder. That is, consideration is given so that aluminum powder isprevented from settling by limiting the content of the naturalpolysaccharides for thickening, but sometimes the discharging amount islittle and sometimes splitting (an amount of ink in a part where theball contacts a paper face is so little as to cause the ink to stay onlyat both sides thereof and therefore the line looks two) is liable takeplace. Accordingly, the ink has a problem in terms of practical use.

Further, disclosed in Japanese Patent Application Laid-Open No. Hei2-69580 is a low viscosity water based metallic color ink containing aresin emulsion, in which dispersed is a paste of an aluminum powderpigment of which surface is wetted with a solvent of a hydrocarbon mixedwith an ester based wax for rust-prevention. Disclosed in JapanesePatent Application Laid-Open No. Hei 6-313142 is a water based metalliclustrous color ink using a water-soluble dye, in which the content of aninorganic salt has been set to 0.5% by weight or less. Disclosed inJapanese Patent Application Laid-Open No. Sho 63-95277 is a water basedmetallic color ink containing an aluminum powder pigment, an amphotericcompound, a resin emulsion, water, an organic pigment and a metallicsoap. Disclosed in Japanese Patent Application Laid-Open No. Sho58-80368 is a water based metallic color ink for writing instrumentscontaining an aluminum powder pigment, an acrylic resin emulsion, apolyvinyl alcohol and/or cellulose based water-soluble resin and awater-dispersed type pigment.

Disclosed in Japanese Patent Application Laid-Open No. Hei 6-192610 is awater based ink composition for writing instruments containing analuminum pigment, a water-soluble organic solvent and aperfluoroalkylphosphoric ester and/or a perfluoroalkyltrimethylammoniumsalt.

The ink disclosed in Japanese Patent Application Laid-Open No. Hei6-313142 mentioned above reveals a colored metallic lustrous color byusing a water-soluble dye as a colorant. However, a dye penetrates intofibers of paper when the viscosity is lower than that of the inkcomposition for a ballpoint pen shown in Example 2, so that the dyedraws outlines around the lines of the metal powder pigment, or acolored metallic lustrous color having a sufficient intensity is notobtained, and therefore the lines tend to become drawn lines close to asilver color. When a water based colored metallic color ink was actuallyprepared by using aluminum powder in combination with correspondingamounts of a thickener and a colorant (yellow pigment), it was foundthat the ink presented a beautiful golden color and that in actualwriting, a colored metallic color was developed on a paper face whichscarcely absorbs an ink, such as coated paper. On the other hand, whenwriting was carried out on a normal paper face (absorbent paper),particularly a colored paper face (absorbent paper), it was found that acolored metallic lustrous color was displayed immediately after writing.However, there was a problem that the drawn lines were finally turnedclose to a silver color due to fading of the color which was supposed tobe caused by settling of the yellow pigment. Considered as a method forsolving this problem is the method of adding a large amount of a colorpigment to raise a viscosity of the ink to thereby delay a settling rateof the pigment. However, there occurs a problem in terms of storagestability or there is a problem such that stable discharge of the inkfrom the pen tip cannot be obtained.

Further, inks for low viscosity markers and felt tip pens using pigmentsas colorants are disclosed in Japanese Patent Application Laid-Open No.Sho 58-80368, Japanese Patent Application Laid-Open No. Sho 63-95277 andJapanese Patent Application Laid-Open No. Hei 2-69580 each describedabove. Those inks contain resin emulsions also as an essentialcomponent. However, the emulsions are used for a principal purpose ofproviding the drawn lines with a sticking property. For this purpose, afilm-forming emulsion is used and blended in a large amount.

However, when this film-forming emulsion is used for paint markers,which use a so-called porous pen core for a pen tip and a valvemechanism for an ink tank, and which are capable of supplying a lot ofan ink to the pen core at any time, there are scarcely problems.However, when it is used particularly for a ballpoint pen, a water basedballpoint pen in which a space of a flow pass in a ball tip part issmall have easily a reduction in a flowing amount due to dry up at thepen tip and inferior writing because of a film-forming effect of theemulsion.

Further, it is described that the ink shown in Japanese PatentApplication Laid-Open No. Hei 6-192610 described above can use knownwater-soluble dyes, organic pigments and inorganic pigments, but nospecific examples are disclosed.

Accordingly, an object of the present invention is to provide a waterbased ink having a metallic luster for a ballpoint pen using aluminumpowder blended with a thickener in a suitable amount, in which areduction in the flowing amount and splitting are not brought about.

Further, an object of the present invention is to provide a water basedpigment ink having a metallic lustrous color for a ballpoint pencontaining aluminum powder and water-soluble organic solvent, in which ametallic lustrous color having good color development of the pigment isobtained as well in writing on an absorbent paper usually used,particularly a colored absorbent paper and beautiful lines can be drawnand in which a reduction in the flowing amount of the ink is scarcelybrought about.

DISCLOSURE OF THE INVENTION

The water based ink having a metallic lustrous color for a ballpoint penof the present invention comprises a thickener, a water-soluble organicsolvent, water and an aluminum paste prepared by wetting aluminum powderin advance with at least one solvent selected from glycol ethers andglycols. This allows the dispersibility of the aluminum powder to beimproved, beause at least one solvent selected from glycol ethers andglycols is freely miscible with water which is the principal solvent.Therefore, the aluminum powder is evenly dispersed in an ink vehiclecontaining the thickener and the other components, so that splitting isprevented. In addition, the ink flows out suitably from the pen tip of aballpoint pen, and the good writing performance is shown.

Further, the water based pigment ink having a metallic lustrous colorfor a ballpoint pen of the present invention comprises aluminum powder,a water-soluble organic solvent, a pigment, a thickener and a resinemulsion. The resin emulsion is charged into the inside of paper fibersand allows a beautiful colored lustrous color (metallic color) to berevealed by virtue of its filling action of inhibiting the color pigmentfrom settling as is the case with writing on a paper face which scarcelyabsorbs an ink, such as a coated paper.

BEST MODE FOR CARRYING OUT THE INVENTION

The water based ink having a metallic lustrous color for a ballpoint penaccording to the present invention shall be explained below in detail.

The aluminum paste used for the water based ink of the present inventionis prepared by wetting aluminum powder with at least one solventselected from glycol ethers and glycols. An aluminum content in thealuminum paste is 40 to 90% by weight.

Products subjected to rust prevention treatment so that they can be usedfor water based inks are preferred as the aluminum powder, and preferredare products obtained by treating with, for example, phosphoric esters,phosphates and phosphides, vanadates, chromium compounds and dimericacids, or products encapsulated with inorganic or organic protectivefilm (polymer) coats.

The aluminum paste prepared by subjecting the aluminum powder to wettingtreatment with a glycol ether or a glycol includes as commercialproducts, for example, STAPA HYDROLAC PM2, PM8, PM2n.l., PM8n.l.,PM16n.l., PM60n.l., PM65n.l., PM24n.l., BG2, BG8, BG2n.l., BG8n.l.,BG16n.l., BG60n.l., BG65n.l. and BG24n.l., and STAPA HYDROLAC PM CHROMALI, II, IV, VIII and X (all manufactured by ECKART Co., Ltd.).

The content of the aluminum paste in the ink is preferably 1 to 15% byweight based on the whole amount of the ink in terms of an amountconverted to powder. When the content is less than 1% by weight, thelines have poor metallic luster, and when the content exceeds 15% byweight, an adverse effect comes to be exerted on discharge of a fixedamount of the ink.

The thickener used for the water based ink of the present invention isused in order to prevent the aluminum powder from settling and to obtaina viscosity suited to a water based ink for a ballpoint pen. Though thekind thereof is not specifically restricted, desired are products whichscarcely bring about a change in the viscosity with the passage of timeand have a high thickening effect in the water based ink using thealuminum pigment. For example, water-soluble natural polymers producedby a microbiological fermentation method can be given. To be specific,KELZAN, do. AR, T and S, KELTROL, do F, T and K9A48 as xanthan gum,KIA96 as welan gum, KIA 112 and K7C233 as rhamsan gum, KELCOGEL asgellan gum, and RHEOZAN, MEYPOLY as other fermented gums (all availablefrom Sansho Co., Ltd.), and guar gum and its derivatives, and inaddition thereto, HIVISWAKO 103, 104 and 105 as cross-linking typeacrylic acid polymers (all available from Wako Pure Chemical Industries,Ltd.) can be used, and further clay minerals such as silica, magnesiumaluminum silicate, bentonite and hectorite can be used in combinationwith those natural and synthetic polymers.

The content of the thickener in the ink is preferably 0.4 to 1.0% byweight based on the whole amount of the ink. When the content is lessthan 0.4% by weight, the thickener does not sufficiently display aneffect of inhibiting the aluminum powder from settling and the inkbecomes unsuitable for use in a ballpoint pen. On the other hand, whenthe content exceeds 1.0% by weight, the discharging amount of ink isreduced, so that the color is not sufficiently developed.

The water-soluble organic solvent used for the water based ink of thepresent invention is added in order to improve qualities required forthe ink for a ballpoint pen, for example, prevention of dry up at thepen tip and antifreezing of the ink at low temperatures and improvementin smoothness of writing. To be specific, there can be used glycols suchas ethylene glycol, diethylene glycol, triethylene glycol, propyleneglycol, polyethylene glycol, 1,3-butylene glycol, glycerin, diglycerinand derivatives thereof.

Can suitably be added, if necessary, is sequestering agents, pHcontrollers, dispersion aids, sticking agents, defoaming agents,surfactants, preservatives, fungicides, rust preventives, colorpigments, coloring dyes, emulsions and latices.

Water is used as a principal solvent, and pH in the whole ink is setpreferably to about 7.

The aluminum paste used for the water based ink having a metalliclustrous color for a ballpoint pen comprises at least the aluminumpowder wetted in advance with glycol ether or glycol, and this glycolether or glycol is freely miscible with water which is the principalsolvent, so that the aluminum powder has the good dispersibility andhence is homogeneously dispersed in the ink vehicle containing thethickener and the other components. Accordingly, it is presumed that thedischarging amount of the ink from the pen tip of the ballpoint pen issuitable and splitting is prevented.

The water based pigment ink having a metallic lustrous color for aballpoint pen according to the present invention shall be explainedbelow in detail.

Products subjected to rust prevention treatment so that they can be usedfor water based inks are preferred as the aluminum powder used for thewater based pigment ink of the present invention, and preferred areproducts obtained by treating with, for example, phosphoric esters,phosphates and phosphides, vanadates, chromium compounds and dimericacids, or products encapsulated with inorganic or organic protectivefilm (polymer) coats.

The aluminum powder used for the water based pigment ink of the presentinvention is used preferably in the form of an aluminum paste, and thoseprepared by wetting aluminum powder with at least one solvent selectedfrom glycol ethers and glycols are particularly preferred. An aluminumcontent in the aluminum paste is 40 to 90% by weight.

To be specific, the commercial products include STAPA HYDROLAC PM2, PM8,PM2n.l., PM8n.l., PM16n.l., PM60n.l., PM65n.l., PM24n.l., BG2, BG8,BG2n.l., BG8n.l., BG16n.l., BG60n.l., BG65n.l. and BG24n.l., and STAPAHYDROLAC PM CHROMAL I, II, IV, VIII and X (all manufactured by ECKARTCo., Ltd.), and other products include 0500M, WB010, WB0230, 1500MA,1539NA, WB1130 and WX1130 (all manufactured by TOYO ALUMINIUM K.K.), andAW-600, 500B, 520B, 666C, 808C, 7000R, 50F and 21G (all manufactured byAsahi Kasei Metals Co., Ltd.).

The content of the aluminum paste in the ink is preferably 1-15% byweight based on the whole amount of the ink in terms of an amountconverted to powder. When the content is less than 1% by weight, thelines have a poor metallic lustrous color, and when the content exceeds10% by weight, an adverse effect comes to be exerted on discharge of afixed amount of the ink and thus a strong silver color is developed, sothat an impression of the colored metallic lustrous color is not good.Incidentally, when a leafing type (a type in which aluminum particlesare disposed parallel on a coated surface layer) of an aluminum powderis used, it is desirable that the degree of leafing is suitablycontrolled by fatty acid soap or other surfactants.

The component resins of the resin emulsion used in the present inventionshall not specifically be restricted and are preferably the followingones. They include, for example, polymethyl methacrylate,styrene-butadiene copolymers, styrene-acryl copolymers,styrene-(meth)acrylate copolymers, polyvinyl chloride resins,polystyrene, vinylpyridine copolymers, polychloroprene, polyisoprene,polyurethane, polyesters, epoxy resins, melamine resins, acryl resins,benzoguanamine resins and polyvinyl acetate.

Included as well in these polymers are resins obtained by modifying thepolymers described above with trace components by graft polymerizationand cross-linking, the names of which are prefixed by "modified","cross-linking type" and "self cross-linkable type".

To be specific, commercial products include Nipol LX303 and LX382manufactured by Nippon Zeon Co., Ltd. as styrene-butadiene copolymeremulsions, G151 manufactured by Nippon Zeon Co., Ltd. as polyvinylchloride, MH5055 manufactured by Nippon Zeon Co., Ltd., SX863, SX864 andSX865 manufactured by Japan Synthetic Rubber Co., Ltd., OP-62 and OP-84Jmanufactured by Rohm & Haas Co., Ltd., Microgel E-2002, E-5001, E-5002,E-1001, E-1002, E-3101 and E-6000 manufactured by NIPPON PAINT CO.,LTD., and MOWINYL 749J, 749S, 871, 970 and 972 manufactured by HoechstGosei Co., Ltd. as styrene-acryl copolymers and styrene-(meth)acrylatecopolymers, and J-790 and J-780 manufactured by Johnson Polymer Co.,Ltd., Experimental Emulsion E-357 and E-1630 and Primal B-85, WL-51,WL-71, WL-81, WL-91, WL-93, B-88 and NTS-2923 manufactured by Rohm &Haas Co., Ltd., T-371 manufactured by Japan Synthetic Rubber Co., Ltd.,MOWINYL 742N manufactured by Hoechst Gosei Co., Ltd., and MP seriesmanufactured by Soken Chemical Co., Ltd. as poly(meth)acryls.

The resin emulsion used for the water based pigment ink of the presentinvention has an average particle diameter falling preferably in a rangeof 0.03 to 0.6 μm, more preferably 0.08 to 0.6 μm. When the averageparticle diameter is less than 0.03 μm, the emulsion is freely absorbedinto a absorbent paper face, and a filling effect of preventing thepigment from penetrating into the inside of the paper face is hardlydisplayed. On the other hand, when the average particle diameter exceeds0.6 μm, the emulsion stays in a condition in which the emulsion isscarcely absorbed (to be difficult to pass through gaps between fibersof paper) into a paper face of absorbent paper, and further, a problemcomes to occur in discharging a ballpoint pen ink. As a result, afilling effect of preventing the pigment from penetrating into theinside of a paper face is hardly displayed as is the case with anaverage particle diameter of less than 0.03 μm.

Further, the resin emulsion used for the water based pigment ink of thepresent invention has preferably no film-forming property at roomtemperature and has preferably a high Tg. A minimum film-formingtemperature means a temperature shown in a boundary between a uniformcontinuous film part and a cloudy part, wherein the emulsion is appliedto a stainless steel plate of a temperature gradient test apparatus in athickness of 0.3 mm and the condition of the film is observed afterdryed (with silica gel) hermetically.

If the emulsion having a film-forming property at room temperature, thatis, the emulsion having a minimum film-forming temperature of lower than40° C. is used, imparted to the drawn lines is a sticking property byvirtue of a film-forming action thereof, but when it is used for an inkfor a ballpoint pen, a reduction in the discharging amount of the inkdue to drying at the pen tip and inferior writing are likely to occurbecause of the sticking property, and therefore the emulsion is unsuitedfor use as an ink for a ballpoint pen.

When the resin emulsion used for the water based pigment ink of thepresent invention uses an emulsifier, the emulsifier has to be suitablyselected so that an adverse effect is not exerted on the thickener andthe dispersed color pigment each of which shall be described later.

Further, the ink which is excellent in settling stability and storagestability can be provided as well by selecting an emulsion having a lowspecific gravity containing hollow particle.

The resin emulsion used for the water based pigment ink of the presentinvention having no film-forming property at room temperature iscontained preferably in an amount of 1 to 10% by weight in terms of asolid content. When the resin emulsion having a minimum film-formingtemperature of room temperature or lower is used, it can be used in anamount of 5% by weight or less in terms of a solid content.

The resin emulsions having different physical properties such as Tg canfreely be selected according to purposes; for example, the ink isprovided with a sticking property by using an emulsion having a low Tg;and the ink which scarcely exerts an adverse effect on dry up caused bydrying at the pen tip can be provided by using the emulsion having ahigh Tg because of less film-forming ability. Further, the ink which isexcellent in settling stability and storage stability can be provided aswell by selecting a latex emulsion containing hollow particles having alow specific gravity.

The thickener used for the water based pigment ink of the presentinvention is used in order to prevent the aluminum powder from settlingand obtain a viscosity suited to an ink for a ballpoint pen. Though thekind thereof is not specifically restricted, preferred are thethickeners which scarcely cause a change in a viscosity with the passageof time and have a high thickening effect in the water based pigment inkusing the aluminum powder.

In particular, products which are reduced in a viscosity of the ink byshearing brought about with rotation of the ball (pen tip) are preferredas the thickener mainly used. They include, for example, water-solublenatural polymers produced by a microbiological fermentation method. Tobe specific, KELZAN, do. AR, T and S, KELTROL, do. F and T and K9A48 asxanthane gum, KIA96 as welan gum, KIA112 and K7C233 as rhamsan gum,KELCOGEL as gellan gum, and RHEOZAN, MEYPOLY as other fermented gums(all available from Sansho Co., Ltd.), guar gum and its derivatives, andin addition thereto, HIVISWAKO 103, 104 and 105 as cross-linking typeacrylic acid polymers (all available from Wako Pure Chemical Industries,Ltd.). Further, clay minerals such as silica, magnesium aluminumsilicate, bentonite and hectorite can be used in combination with thosenatural and synthetic polymers.

The content of the thickener in the ink is preferably 0.4 to 1.0% byweight based on the whole amount of the ink. When the content is lessthan 0.4% by weight, the thickener does not sufficiently display aneffect of inhibiting the aluminum powder from settling, and the inkbecomes unsuitable for use in a ballpoint pen. On the other hand, whenthe content exceeds 1.0% by weight, the discharging amount of ink isreduced, so that the color is not sufficiently developed.

Solvents which have so far been used for water based pigment inks areused as the water-soluble organic solvent for the ink of the presentinvention. To be specific, they can include glycols such as ethyleneglycol, diethylene glycol, triethylene glycol, propylene glycol,polyethylene glycol, 1,3-butylene glycol, glycerin, diglycerin andderivatives thereof. These solvents show an effect of improvingqualities required for the ink for a ballpoint pen, for example,prevention of dry up at the pen tip and antifreezing of the ink at lowtemperatures, and an improvement in the writing smoothness.

The content of the water-soluble organic solvent in the ink ispreferably 5 to 40% by weight based on the whole amount of the ink. Whenthe content is less than 5% by weight, the effects such as prevention ofdry up at the pen tip and antifreezing of the ink at low temperatures,and an improvement in the writing smoothness are not sufficientlydisplayed, and the ink is unsuited to use for a ballpoint pen. On theother hand, when the content exceeds 40% by weight, the dischargingamount of ink is reduced, the color is not sufficiently developed and ittakes longer time for the drawn lines to dry.

The color pigment used for the water based pigment ink of the presentinvention can freely be selected from known pigments which have so farbeen used for water based pigment inks. These pigments are dispersedpreferably by means of a paint shaker or a bead mill in a system inwhich the resin, the surfactant, the solvent and the like are added inadvance, or preferably used in the form of a toner in which a processedpigment (the pigment with a resin and a surfactant adsorbed) isdispersed with stirring. The pigment used has preferably an averageparticle diameter falling in a range of 0.03 to 0.3 μm. When the averageparticle diameter is less than 0.03 μm, the pigment particles are easilyabsorbed freely into a paper face of absorbent paper, and apenetration-preventing effect produced by a filling effect of theemulsion is hardly exhibited enough. On the other hand, when the averageparticle diameter exceeds 0.3 μm, the dispersion stability of the toneritself is usually deteriorated, and therefore an adverse effect isliable to be exerted as well on the ink to which the toner is added.

The content of the pigment in the ink is preferably 0.5 to 15% by weightbased on the whole amount of the ink. When the content is less than 0.5%by weight, the color of the pigment is insufficiently developed, and itis difficult to obtain colored metallic luster. On the other hand, whenthe content exceeds 15% by weight, the color of the pigment is toointensely developed, and therefore the lines having a poor lustrousquality are drawn.

Can suitably be added, if necessary, is sequestering agents, pHcontrollers, dispersion aids, sticking agents, defoaming agents,surfactants, preservatives, fungicides and rust preventives.

Water is used as the principal solvent, and pH in the whole ink is setpreferably to about 7.

The color pigment is prevented from penetrating into a paper face inexcess by a filling effect produced by allowing the resin emulsion usedfor the water based pigment ink having a metallic lustrous color for aballpoint pen to penetrate into an absorbent face and to be charged intogaps between fibers of paper. Accordingly, it is presumed that thealuminum powder and the color pigment are present efficiently on a paperface, so that a beautiful metallic lustrous color is presented.

EXAMPLES

The present invention shall be explained below with reference toexamples.

Example 1

    ______________________________________                                        Silver ink:                                                                   ______________________________________                                        Aluminum paste        14     parts by weight                                  "STAPA HYDROLAC PM Chromal VIII"                                              [manufactured by ECKART Co., Ltd.;                                            aluminum powder content: about                                                70% by weight (containing propylene                                           glycol monomethyl ether as a solvent)]                                        Water                 40.2   parts by weight                                  Propylene glycol      12     parts by weight                                  Glycerin              3      parts by weight                                  Thickener             30     parts by weight                                  2% aqueous solution of "Rheozan"                                              (brand name, manufactured by                                                  Sansho Co., Ltd.)                                                             Preservative          0.15   part by weight                                   "Hokucide N100" (brand name,                                                  manufactured by Hokko Chemical                                                Industry Co., Ltd.)                                                           Rust Preventive: benzotriazole                                                                      0.2    part by weight                                   Sequestering agent    0.3    part by weight                                   "Zonon D" (brand name, manufactured                                           by Daiichi Kagaku Yakuhin Co., Ltd.)                                          2-Amino-2-methyl-1-propanol                                                                         0.15   part by weight                                   "AMP-90" (brand name, manufactured                                            by ANGUS Chemical Company, Ltd.                                               (containing about 10% of water)                                               ______________________________________                                    

The components other than the thickener out of the respective componentsdescribed above were mixed for one hour by means of a labo mixer, andthen the thickener prepared in advance in the form of a 2% aqueoussolution was added, followed by stirring and mixing again for one hour,whereby an ink having a viscosity of 3200 centipoise (E type viscometer,1 rpm, 25° C.) and a pH of 7.2 was obtained.

Example 2

    ______________________________________                                        Golden ink:                                                                   ______________________________________                                        Aluminum paste       5      parts by weight                                   "STAPA HYDROLAC BG8n.1."                                                      [manufactured by ECKART Co., Ltd.;                                            aluminum powder content: about                                                70% by weight (containing water and                                           butyl glycol as solvents)]                                                    Water                26.7   parts by weight                                   Thickener            25     parts by weight                                   Xanthan gum; 2% aqueous solution                                              of "Keltrol" (brand name,                                                     manufactured by Sansho Co., Ltd.)                                             Ethylene glycol      15     parts by weight                                   Preservative         0.15   part by weight                                    "Hokucide N100" (brand name,                                                  manufactured by Hokko Chemical                                                Industry Co., Ltd.)                                                           Rust preventive: benzotriazole                                                                     0.2    part by weight                                    Sequestering agent   0.15   part by weight                                    "Zonon D" (brand name, manufactured                                           by Daiichi Kagaku Yakuhin Co., Ltd.)                                          2-Amino-2-methyl-1-propanol                                                                        0.1    part by weight                                    "AMP-90" [brand name, manufactured                                            by ANGUS Chemical Company, Ltd.                                               (containing about 10% of water)]                                              Acrylic emulsion     7      parts by weight                                   "Johncryl J-7001" (Johnson Polymer                                            Co., Ltd., solid content: 42%)                                                Yellow pigment toner 20     parts by weight                                   (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                "C.I. Pigment Yellow 137")                                                    Red pigment toner    0.7    part by weight                                    (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                "C.I. Pigment Red 17")                                                        ______________________________________                                    

The respective color pigment toners described above were obtained bydispersing the prescribed amounts of the components for about 30 minutesby means of a bead mill. The pigments obtained by dispersing had anaverage particle diameter of about 100 to 200 nm.

The components other than the thickener out of the respective componentsdescribed above were stirred and mixed for one hour by means of a labomixer, and then the thickener prepared in advance in the form of a 2%aqueous solution was added, followed by stirring and mixing again forone hour, whereby an ink having a viscosity of 3000 centipoises (E typeviscometer, 1 rpm, 25° C.) and a pH of 7.1 was obtained.

Comparative Example 1

An ink was prepared in the same composition as in Example 1, except thatthe aluminum paste was replaced with "AW-600" (manufactured by AsahiKasei Metals Co., Ltd., containing 69% by weight of aluminum powder andin addition thereto, containing water and mineral spirits).

Comparative Example 2

An ink was prepared in the same composition as in Example 2, except that5 parts by weight of the aluminum paste used in Example 2 was replacedwith "WB1130" (manufactured by TOYO ALUMINIUM K.K., containing 67% byweight of aluminum powder and in addition thereto, containing mineralspirits).

The writing performances of the water based inks obtained in Examples 1and 2 and Comparative Examples 1 and 2 were tested by the followingmethod.

The respective inks were charged into polypropylene holder refills(UMR-5) of ballpoint pens "UM-100" manufactured by MITSUBISHI PENCILCO., LTD. to produce ballpoint pens for evaluation through a prescribedassembly procedure.

A 0.7 mm ball tip was used for the pen tip, and the pen tip obtained byenlarging the respective clearances of the ball, the holder and thechannel for a high viscosity was used.

Spirals having a diameter of about 2 cm were drawn on wood free paper(JIS P32012 writing paper A) by handwriting at a writing angle of about60° by means of the ballpoint pens for evaluation described above.

In this case, the writing speed was set up to approximately three levels[writing 1/4 spiral per second (slow), writing 1 spiral per second(standard) and writing 2 spirals per second (fast)].

The writing performances of the drawn lines were evaluated according tothe following criteria:

⊚: capable of writing well

∘: no starving and splitting observed and capable of writing (a littlesmall discharging amount of ink)

Δ: starving caused (small discharging amount of ink)

▴: splitting caused (small discharging amount of ink)

X: impossible to write

The test results are shown in Table 1.

                  TABLE 1                                                         ______________________________________                                                 Writing performance                                                           1*         2*     3*                                                 ______________________________________                                        Example 1  ⊚                                                                           ⊚                                                                     ⊚                               Example 2  ⊚                                                                           ⊚                                                                     ⊚                               Comparative                                                                              Δ      ▴                                                                     ▴                               Example 1                                                                     Comparative                                                                              Δ      ▴                                                                     ▴                               Example 2                                                                     ______________________________________                                         *Writing speed:                                                               1 1/4 spiral/second                                                           2 1 spiral/second                                                             3 2 spirals/second                                                       

It can be found from the results obtained in Examples 1 and 2 that whenthe aluminum pastes wetted with the solvent selected from glycol ethersand glycols were used, the amount of the ink discharged from the tip ofthe ballpoint pen is optimized even at a fast writing speed as is thecase with the slow writing speed and that starving and splitting do notoccur.

In contrast with this, it can be found that when the conventionalaluminum pastes wetted with mineral spirits which is not soluble inwater as shown in Comparative Examples 1 and 2 were used, the amount ofthe ink discharged from the tip of the ballpoint pen is small and thusstarving occurs in the drawn lines even when the writing speed is slow.

The respective color pigment toners used in the following examples wereobtained by dispersing the prescribed amounts of the components forabout 30 minutes by means of a bead mill. The pigments obtained bydispersing had an average particle diameter of about 100 to 200 nm.

Example 3

    ______________________________________                                        Golden ink:                                                                   ______________________________________                                        Aluminum paste        3      parts by weight                                  "STAPA HYDROLAC PM Chromal VIII"                                              [manufactured by ECKART Co., Ltd.;                                            aluminum powder content: about                                                70% by weight (containing propylene                                           glycol monomethyl ether as a solvent)]                                        Purified water        11.5   parts by weight                                  Propylene glycol      12     parts by weight                                  Glycerin              3      parts by weight                                  Thickener             30     parts by weight                                  2% aqueous solution of "Rheozan"                                              (brand name, manufactured by                                                  Sansho Co., Ltd.)                                                             Preservative          0.15   part by weight                                   "Hokucide N100" (brand name,                                                  manufactured by Hokko Chemical                                                Industry Co., Ltd.)                                                           Rust preventive: benzotriazole                                                                      0.2    part by weight                                   Sequestering agent    0.3    part by weight                                   "Zonon D" (brand name, manufactured                                           by Daiichi Kagaku Yakuhin Co., Ltd.)                                          2-Amino-2-methyl-1-propanol                                                                         0.15   part by weight                                   "AMP-90" (brand name, manufactured                                            by ANGUS Chemical Company, Ltd.;                                              containing about 10% of water)                                                Acrylic emulsion      19     parts by weight                                  "Johncryl J-780" (brand name,                                                 manufactured by Johnson Polymer Co.,                                          Ltd.; solid content: 42%; average                                             particle diameter: 0.1 μm; minimum film-                                   forming temperature: 50° C. or higher)                                 Yellow pigment toner  20     parts by weight                                  (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                C.I. Pigment Yellow 137)                                                      Red pigment toner     0.7    part by weight                                   (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                C.I. Pigment Red 17)                                                          ______________________________________                                    

The respective color pigment toners described above were obtained bydispersing the prescribed amounts of the components for about 30 minutesby means of a bead mill. The pigments contained in these pigment tonershad an average particle diameter of about 100 to 200 nm.

The components other than the thickener out of the respective componentsdescribed above were stirred and mixed for one hour by means of a labomixer, and then the thickener prepared in advance in the form of a 2%aqueous solution was added, followed by stirring and mixing again forone hour, whereby an ink having a viscosity of 3300 centipoises (E typeviscometer, 1 rpm, 25° C.) was obtained.

Example 4

    ______________________________________                                        Blue metallic ink:                                                            ______________________________________                                        Aluminum paste       5      parts by weight                                   "STAPA HYDROLAC BG8n.1."                                                      [manufactured by ECKART Co., Ltd.;                                            aluminum powder content: about                                                70% by weight (containing butyl                                               glycol as a solvent)]                                                         Purified water       25.9   parts by weight                                   Ethylene glycol      15     parts by weight                                   Thickener            25     parts by weight                                   2% aqueous solution of "Keltrol"                                              (brand name, manufactured by                                                  Sansho Co., Ltd.)                                                             Preservative         0.15   part by weight                                    "Hokucide N100" (brand name,                                                  manufactured by Hokko Chemical                                                Industry Co., Ltd.)                                                           Rust preventive: benzotriazole                                                                     0.2    part by weight                                    Sequestering agent   0.15   part by weight                                    "Zonon D" (brand name, manufactured                                           by Daiichi Kagaku Yakuhin Co., Ltd.)                                          2-Amino-2-methyl-1-propanol                                                                        0.1    part by weight                                    "AMP-90" (brand name, manufactured                                            by ANGUS Chemical Company, Ltd.;                                              containing about 10% of water)                                                Potash soap A        0.5    part by weight                                    (manufactured by Kyoeisha Chemical                                            Co., Ltd.)                                                                    Cross-linking type styrene-acryl                                                                   8      parts by weight                                   emulsion                                                                      "SX-860" (brand name, manufactured                                            by Japan Synthetic Rubber Co., Ltd.;                                          solid content: 40%; average particle                                          diameter: 0.50 μm; no film-forming                                         ability at room temperature)                                                  Blue pigment toner   20     parts by weight                                   (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                "C.I. Pigment Blue 15")                                                       ______________________________________                                    

The blue pigment toner described above was obtained by dispersing theprescribed amounts of the components for about 30 minutes by means of abead mill. The pigments obtained by dispersing had an average particlediameter of about 100 to 200 nm.

The components other than the thickener out of the respective componentsdescribed above were stirred and mixed for one hour by means of a labomixer, and then the thickener prepared in advance in the form of a 2%aqueous solution was added, followed by stirring and mixing again forone hour, whereby an ink having a viscosity of 3200 centipoises (E typeviscometer, 1 rpm, 25° C.) was obtained.

Example 5

    ______________________________________                                        Green metallic ink:                                                           ______________________________________                                        Aluminum paste         9      parts by weight                                 "WX1130" [(manufactured by TOYO                                               ALUMINIUM K.K.; aluminum powder                                               content: about 56% by weight                                                  (containing mineral spirits and isopropyl                                     alcohol as solvents)]                                                         Purified water         14     parts by weight                                 Propylene glycol       15     parts by weight                                 Thickener              45     parts by weight                                 1% aqueous solution of "HIVISWAKO                                             105" (manufactured by Wako Pure                                               Chemical Industries, Ltd.)                                                    Preservative           0.15   part by weight                                  "Hokucide N100" (brand name,                                                  manufactured by Hokko Chemical                                                Industry Co., Ltd.)                                                           Rust preventive: benzotriazole                                                                       0.2    part by weight                                  Sequestering agent     0.15   part by weight                                  "Zonon D" (brand name, manufactured                                           by Daiichi Kagaku Yakuhin Co., Ltd.)                                          2-Amino-2-methyl-1-propanol                                                                          0.1    part by weight                                  "AMP-90" (brand name, manufactured                                            by ANGUS Chemical Company, Ltd.;                                              containing about 10% of water)                                                Styrene-acryl emulsion 6      parts by weight                                 "ROPAQUE HP-91" (brand name, manufactured                                     by Rohm & Haas Co., Ltd.; solid                                               content: 53%; average particle                                                diameter: 1 μm; no film-forming                                            ability at room temperature)                                                  Blue pigment toner     0.4    part by weight                                  (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                "C.I. Pigment Blue 15")                                                       Yellow pigment toner   10     parts by weight                                 (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                "C.I. Pigment Yellow 137")                                                    ______________________________________                                    

The components other than the thickener out of the respective componentsdescribed above were stirred and mixed for one hour by means of a labomixer, and then the thickener prepared and neutralized in advance in theform of a 1% aqueous solution was added, followed by stirring and mixingagain for one hour, whereby an ink having a viscosity of 2500centipoises (E type viscometer, 1 rpm, 25° C.) was obtained.

Example 6

    ______________________________________                                        Purple metallic ink:                                                          ______________________________________                                        Aluminum paste        3      parts by weight                                  "AW-808" [(brand name, manufactured                                           by Asahi Kasei Metals Co., Ltd.;                                              aluminum powder content: about 72%                                            by weight (containing mineral spirits                                         as a solvent)]                                                                Purified water        24.8   parts by weight                                  Propylene glycol      21.3   parts by weight                                  Glycerin              3      parts by weight                                  Thickener             30     parts by weight                                  2% aqueous solution of "Rheozan"                                              (brand name, manufactured by                                                  Sansho Co., Ltd.)                                                             Preservative          0.15   part by weight                                   "Hokucide N100" (brand name,                                                  manufactured by Hokko Chemical                                                Industry Co., Ltd.)                                                           Rust preventive: benzotriazole                                                                      0.2    part by weight                                   Sequestering agent    0.3    part by weight                                   "Zonon D" (brand name, manufactured                                           by Daiichi Kagaku Yakuhin Co., Ltd.)                                          2-Amino-2-methyl-1-propanol                                                                         0.15   part by weight                                   "AMP-90" (brand name, manufactured                                            by ANGUS Chemical Company, Ltd.;                                              containing about 10% of water)                                                Acrylic emulsion      6.5    parts by weight                                  "Johncryl J-390" (brand name,                                                 manufactured by Johnson Polymer Co.,                                          Ltd.; solid content: 46%; average                                             particle diameter: 0.09 μm; minimum film-                                  forming temperature: lower than 5° C.)                                 Blue pigment toner    0.6    part by weight                                   (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                "C.I. Pigment Blue 15")                                                       Red pigment toner     10     parts by weight                                  (aqueous toner dispersed with                                                 acryl resin, containing 15% of                                                "C.I. Pigment Red 17")                                                        ______________________________________                                    

The components other than the thickener out of the respective componentsdescribed above were stirred and mixed for one hour by means of a labomixer, and then the thickener prepared and neutralized in advance in theform of a 1% aqueous solution was added, followed by stirring and mixingagain for one hour, whereby an ink having a viscosity of 3300centipoises (E type viscometer, 1 rpm, 25° C.) was obtained.

Comparative Example 3

An ink was prepared in the same composition as in Example 3, except thatpurified water was substituted for the acrylic emulsion, whereby the inkhaving a viscosity of 3000 centipoises (E type viscometer, 1 rpm, 25°C.) was obtained.

Comparative Example 4

An ink was prepared in the same composition as in Example 4, except thatpurified water was substituted for the cross-linking type styrene-acrylemulsion, whereby the ink having a viscosity of 2700 centipoises (E typeviscometer, 1 rpm, 25° C.) was obtained.

Comparative Example 5

An ink was prepared in the same composition as in Example 5, except thatpurified water was substituted for the cross-linking type styrene-acrylemulsion, whereby the ink having a viscosity of 2400 centipoises (E typeviscometer, 1 rpm, 25° C.) was obtained.

Comparative Example 6

An ink was prepared in the same composition as in Example 6, except thatpurified water was substituted for the cross-linking type styrene-acrylemulsion, whereby the ink having a viscosity of 2900 centipoises (E typeviscometer, 1 rpm, 25° C.) was obtained.

Comparative Example 7

An ink was prepared in the same composition as in Example 6, except thatthe amount of the acrylic emulsion used in Example 6 was increased to 15parts by weight, and the purified water was decreased in an amount bythe increment, whereby the ink having a viscosity of 3400 centipoises (Etype viscometer, 1 rpm, 25° C.) was obtained.

The writing performances of the water based pigment inks obtained inExamples 3 to 6 and Comparative Examples 3 to 7 were tested by thefollowing method.

The respective inks were charged into polypropylene holder refills(UMR-5) of ballpoint pens UM-100 manufactured by MITSUBISHI PENCIL CO.,LTD. to produce ballpoint pens A for evaluation through a prescribedassembly procedure.

A 0.7 mm ball tip was used for the pen tip, and the pen tip obtained byenlarging the respective clearances of the ball, the holder and thechannel for a high viscosity was used.

A part of ballpoint pens A for evaluation was left lying horizontally ina cap-off condition for a week in an air-conditioned chamber of atemperature of 25° C. and a humidity of 65%. The samples obtained afterhaving been left for a week were designated as ballpoint pens B forevaluation.

With respect to the conditions for a writing performance test, ballpointpens A for evaluation described above were used for writing on a coatedpaper (non-absorbent paper) and a black simili paper (absorbent paper),and ballpoint pens B for evaluation were used for drawing 100 spirallines having a diameter of about 3 cm by handwriting on a black similipaper (absorpbent paper) at a writing angle of about 60°.

The writing performances of the drawn lines were evaluated according tothe following criteria:

Evaluation 1: writing test with ballpoint pens A for evaluation;

The whole drawn line conditions were evaluated with eyes after dryingthe drawn lines.

∘: beautiful colored metallic color

: a lot of color turned pale and slightly thin colored metallic color

Δ: silver color observed partially

▴: considerably close to silver color

X: almost silver color

Evaluation 2: writing test with ballpoint pens B for evaluation and anaging stability test in leaving the pens lying with the cap off;

comparison with ballpoint pens A for evaluation

∘: same drawn lines as with ballpoint pens A for evaluation (initial)

Δ: starving of the drawn lines and a reduction in the discharging amounttake place in initial writing but the discharging amount recovers aswriting is continued

▴: drawn lines become starved and the discharging amount is reduced

X: impossible to write

The test results are shown in Table 2.

                  TABLE 2                                                         ______________________________________                                                Writing performance                                                           Evaluation 1     Evaluation 2                                                            Black simili                                                                            Black simili                                             Coated paper                                                                             paper     paper                                                    (non-absorbent                                                                           (absorbent                                                                              (absorbent                                               paper)     paper)    paper)                                           ______________________________________                                        Example 3 ◯                                                                              ◯                                                                           ◯                                Example 4 ◯                                                                              ◯                                                                           ◯                                Example 5 ◯                                                                                                                                                        ◯                                Example 6 ◯                                                                              ◯                                                                           Δ                                      Comparative                                                                             ◯                                                                              ▴                                                                        ◯                                Example 3                                                                     Comparative                                                                             ◯                                                                              X         ◯                                Example 4                                                                     Comparative                                                                             ◯                                                                              X         ◯                                Example 5                                                                     Comparative                                                                             ◯                                                                              X         ◯                                Example 6                                                                     Comparative                                                                             ◯                                                                              ◯                                                                           X                                            Example 7                                                                     ______________________________________                                    

Results of Evaluation 1

It can be found from the results of Examples 3, 4 and 6 that beautifulcolored metallic colors are revealed on a black simili paper which is anabsorbent paper as well as on a coated paper which is a non-absorbentpaper by adding the resin emulsions. In Example 5, the resin emulsionhas a particle diameter which deviates from a suitable range, andtherefore the results thereof are a little inferior to the resultsobtained in the other examples. In contrast with this, it can be foundthat since the inks prepared in Comparative Examples 3 to 6 do notcontain the resin emulsions, the pigments of colorants are liable tosettle before drying the drawn lines, and therefore the drawn lines areclose to or scarcely different from the silver drawn lines.

Results of Evaluation 2

The inks prepared in Examples 3 to 5 and Comparative Examples 3 to 6contain the resin emulsions having no film forming ability at roomtemperature or do not contain the resin emulsions, and therefore theballpoint pens obtained after having been left lying with the cap offcan draw lines which are not different from those drawn with the samples(ballpoint pens A) before being left lying. It can be found that the inkprepared in Example 6 has a lower film-forming temperature than roomtemperature and therefore is inferior in a writing performance afterstored with the cap off as compared with the other inks.

In Comparative Example 7, while the drawn lines have a good colordevelopability on an absorbent paper, inferior writing is brought aboutby dry up at the pen tip due to the film-forming ability of the emulsioncontained in a large amount.

Industrial Applicability

The water based ink having a metallic lustrous color for a ballpoint penaccording to the present invention uses an aluminum paste prepared bywetting aluminum powder in advance with at least one solvent selectedfrom glycol ethers and glycols, so that the dispersibility of thealuminum powder is improved because this solvent is freely miscible withwater which is the principal solvent. Accordingly, the aluminum powderis evenly dispersed in an ink vehicle containing the thickener and theother components, and splitting is prevented. In addition, the inksuitably flows out from the pen tip of a ballpoint pen, and the goodwriting performance is shown.

Further, the resin emulsion in the water based pigment ink having ametallic lustrous color for a ballpoint pen according to the presentinvention is charged into the inside of paper fibers to prevent as afilling the color pigment from settling. As a result, the effect that abeautiful colored lustrous color (metallic color) is revealed isexhibited as is the case with writing on a paper face which scarcelyabsorbs an ink, such as a coated paper.

What is claimed is:
 1. A water based ink having a metallic lustrouscolor for a ballpoint pen comprising a thickener, a water-solubleorganic solvent, water and an aluminum paste prepared by wettingaluminum powder in advance with at least one solvent selected from thegroup consisting of glycol ethers and glycols.
 2. The water based inkhaving a metallic lustrous color for a ballpoint pen as described inclaim 1, wherein said glycol ether is propylene glycol monomethyl ether.3. The water based ink having a metallic lustrous color for a ballpointpen as described in claim 1, wherein said glycol is butylene glycol orpropylene glycol.
 4. The water based ink having a metallic lustrouscolor for a ballpoint pen as described in claim 1, wherein the contentof said aluminum paste in the ink is 1 to 15% by weight based on thewhole amount of the ink in terms of an amount converted to powder. 5.The water based ink having a metallic lustrous color for a ballpoint penas described in claim 1, wherein the content of said thickener in theink is 0.4 to 1.0% by weight based on the whole amount of the ink.
 6. Awater based pigment ink having a metallic lustrous color for a ballpointpen comprising aluminum powder, a water-soluble organic solvent, apigment, a thickener and a resin emulsion.
 7. The water based pigmentink having a metallic lustrous color for a ballpoint pen as described inclaim 6, wherein said resin emulsion has an average particle diameter of0.03 to 0.6 μm.
 8. The water based pigment ink having a metalliclustrous color for a ballpoint pen as described in claim 6, wherein saidresin emulsion has no film-forming property at room temperature.
 9. Thewater based pigment ink having a metallic lustrous color for a ballpointpen as described in claim 7, wherein said resin emulsion has nofilm-forming property at room temperature.
 10. The water based pigmentink having a metallic lustrous color for a ballpoint pen as described inclaim 8, wherein the content of said resin emulsion in the ink is 1 to10% by weight based on the whole amount of the ink in terms of a solidcontent.
 11. The water based pigment ink having a metallic lustrouscolor for a ballpoint pen as described in claim 10, wherein the contentof said resin emulsion in the ink is 1 to 10% by weight based on thewhole amount of the ink in terms of a solid content.
 12. The water basedpigment ink having a metallic lustrous color for a ballpoint pen asdescribed in claim 7, wherein said resin emulsion has a lowestfilm-forming temperature of 40° C. or higher.
 13. The water basedpigment ink having a metallic lustrous color for a ballpoint pen asdescribed in claim 6, wherein said resin emulsion has a lowestfilm-forming temperature of 40° C. or higher.
 14. The water basedpigment ink having a metallic lustrous color for a ballpoint pen asdescribed in claim 9, wherein said resin emulsion has a lowestfilm-forming temperature of 40° C. or higher.
 15. The water basedpigment ink having a metallic lustrous color for a ballpoint pen asdescribed in claim 10, wherein said resin emulsion has a lowestfilm-forming temperature of 40° C. or higher.
 16. The water basedpigment ink having a metallic lustrous color for a ballpoint pen asdescribed in claim 11, wherein said resin emulsion has a lowestfilm-forming temperature of 40° C. or higher.
 17. The water basedpigment ink having a metallic lustrous color for a ballpoint pen asdescribed in claim 6, wherein said aluminum powder is wetted with atleast one solvent selected from the group consisting of glycol ethersand glycols.
 18. The water based pigment ink having a metallic lustrouscolor for a ballpoint pen as described in claim 6, wherein the contentof said thickener in the ink is 0.4 to 1.0% by weight based on the wholeamount of the ink.
 19. The water based pigment ink having a metalliclustrous color for a ballpoint pen as described in claim 6, wherein thecontent of said water-soluble organic solvent in the ink is 5 to 40% byweight based on the whole amount of the ink.
 20. The water based pigmentink having a metallic lustrous color for a ballpoint pen as described inclaim 6, wherein said pigment has an average particle diameter of 0.03to 0.3 μm.
 21. The water based pigment ink having a metallic lustrouscolor for a ballpoint pen as described in claim 6, wherein the contentof said pigment in the ink is 0.5 to 15% by weight based on the wholeamount of the ink.
 22. The water based pigment ink having a metalliclustrous color for a ballpoint pen as described in claim 20, wherein thecontent of said pigment in the ink is 0.5 to 15% by weight based on thewhole amount of the ink.